Cellular Distribution of Metals in a Liverwort and a Moss Transplanted to Two Streams of Differing Acidity G. Thiébaut & L. Giamberini & J. Ghanbaja Received: 21 October 2007 / Accepted: 22 February 2008 / Published online: 19 March 2008 # Springer Science + Business Media B.V. 2008 Abstract To investigate the consequences of acidifi- cation and metal accumulation on the biology of aquatic bryophytes, the acid-tolerant liverwort Scapa- nia undulata (L.) Dum. and the acid-sensitive moss Rhynchostegium riparioides (Hedw.) Cardot were transplanted from one stream to two other streams of differing acidity (pH 5.20 and 6.38). The bryophytes were collected in a circumneutral (pH 6.57) stream in the Vosges Mountains. Metal accumulation was semi- quantitatively measured in shoots by energy disper- sive TEM X-ray spectroscopy (EDXS). After 1 month, the two species remained green without alteration signs. Although no marked ultrastructural damage was observed in either species, some cells seemed to be necrotic, with flattened chloroplasts, in R. ripar- ioides. Lipid droplet accumulation was observed in some leaf cells of S.undulata when transplanted to the most acidic stream. Metal was mostly localised in the cell wall, and was only sometimes detected in small vacuoles. Under acidic conditions, R. riparioides showed the highest relative amount of Al and the lowest amount of Fe, whereas the acid-tolerant bryophyte species S. undulata contained more Fe and less Al. The capability to limit the uptake of metals into the cytoplasm varies according to the bryophyte species. This could be an explanation of the tolerance of S. undulata to acidification. Keywords Acidification . Aluminium . Iron . Bryophytes . X-ray microanalysis 1 Introduction Acid deposition is the main cause of acidification in freshwater (Freedman 1995). The worst situation arises in areas with granitic, sandstone or gneiss substrates, which do not have sufficient free cations to neutralize the acidity deposited (Howells 1990). During the last three decades, numerous studies have focused on the effects of acidification on aquatic biota (e.g., fish, macroinvertebrates, zooplankton, macrophytes and algae). Most of them have revealed deleterious effects of low pH, leading to the loss of biodiversity. In addition to the decline in pH and alkalinity, water toxicity can arise due to increased concentration of H + , heavy metals and aluminium (Al tot and especially the dissolved forms of aluminium), intense removal of metals from soils and from bottom sediments, decrease in sorption by coarsely dispersed suspended material, Water Air Soil Pollut (2008) 192:263–272 DOI 10.1007/s11270-008-9653-8 G. Thiébaut (*) : L. Giamberini LIEBE, University Paul Verlaine-Metz, CNRS UMR 7146, Campus Bridoux, Avenue du Général Delestraint, F-57070 Metz, France e-mail: thiebaut@univ-metz.fr J. Ghanbaja Service Commun de Microscopie Electronique à Transmission, Faculté des Sciences, Université Henri Poincaré, Nancy I, BP 239, F-54506 Vandoeuvre lés Nancy, France